1. Field of the Invention
The present invention relates to a thermal diffuser for uniformly forming a path for close thermal coupling between a mounted electronic component and a surface of a desired thermal conductor in an electronic equipment and to a radiator for radiating heat generated in this electronic component via the thermal diffuser.
2. Description of the Related Art
In recent years, a xe2x80x98tunable OS (optical sender)xe2x80x99 outputting an optical signal with a prescribed wavelength stably and precisely has been in practical use owing to positive application of a technique of precisely controlling operating temperature, and consequently, a WDM (wavelength division multiplexing) transmission method is being positively applied to various transmission systems as well as to relay transmission systems such as submarine optical transmission.
FIG. 9 is a view showing a configuration example of a node in which the tunable OS is mounted.
In FIG. 9, the tunable OS 90 is disposed on a printed circuit board 92 constituting a package attachable to and detachable from a predetermined slot of a shelf (a rack is also acceptable) 91.
FIG. 10 is a view showing the configuration of a radiation system of the tunable OS.
In FIG. 10, inside the tunable OS 90 disposed on the aforesaid printed circuit board 92, provided is a tunable laser diode module (hereinafter, referred to as a xe2x80x98TLD modulexe2x80x99) 94 which is connected with one end of an optical fiber 93 and has close thermal coupling with a case 90C of this tunable OS.
An outer wall opposite to an outer wall facing the printed circuit board 92, out of outer walls of the case 90C, is bonded to one surface of a plate-shaped flat heat pipe 95 and the other surface of this flat heat pipe 95 is bonded to a bottom surface (supposed to be a specific surface on which no radiation fin is formed for simplification here) of a heat sink 96.
The TDL module 94 is composed of the following elements.
a case 94C thermally coupled with the aforesaid case 90C (supposed to be in close contact with it for simplification here)
a peltier 97 having close thermal coupling with the inner wall of the case 94C
a laser diode 98 having close thermal coupling with a predetermined place of a surface of this peltier 97
an optical system 99 optically coupled with an emission port of this laser diode 98 and the aforesaid one end of the optical fiber 93.
In the conventional example having the configuration as described above, a laser beam emitted by the laser diode 98 is led to a not-shown wavelength-division multiplexing part via the optical system 99 and the optical fiber 93. Note that the present invention does not relate to a wavelength of the above laser beam and processing for wavelength-division multiplexing (may include modulation to be executed for each wavelength) executed by the wavelength-division multiplexing part and therefore, the explanations thereof are omitted here.
Meanwhile, heat generated in the laser diode 98 in the process in which the aforesaid laser beam is emitted is once absorbed by the peltier 97 and transferred to the flat heat pipe 95 via the cases 94C and 90C.
Then, the flat heat pipe 95 leads thus transferred heat to each part of the bottom surface of the heat sink 96 via a heat medium (coolant) injected into linear channels which are formed in parallel to each other inside the flat heat pipe 95 as shown by the dotted line in the upper part of FIG. 10 and whose atmospheric pressure is reduced to a predetermined value.
The heat sink 96 radiates thus led heat to an exterior via the radiation fin formed on a predetermined outer wall of the heat sink 96.
In short, the heat generated in the laser diode 98 is absorbed by the peltier 97 according to power supplied to the peltier 97 and radiated to the exterior via the cases 94C and 90C, the flat heat pipe 95, and the heat sink 96.
Therefore, the characteristics of the laser diode 98 and the optical system 99 are stably maintained and the aforesaid wavelength of the laser beam is maintained at a prescribed value as long as temperature is controlled properly via the peltier 97.
Incidentally, in the conventional example described above, the heat generated in the laser diode 98 and transferred to the flat heat pipe 95 via the peltier 97 and the cases 94C and 90C is transferred to the bottom surface of the heat sink 96 via the heat medium injected individually into the plural linear channels which are formed in parallel inside the flat heat pipe 95 as described above.
Therefore, most of the above heat is transferred to the heat sink 96 via the heat medium injected only to specific channels having close thermal coupling with the peltier 97, out of the channels formed inside the flat heat pipe 95, via the cases 90C and 94C.
Consequently, thermal conductivity between the peltier 97 (the laser diode 98) and each part of the bottom surface of the heat sink 96 is not uniform as shown in FIG. 11 and the most of the heat generated in the laser diode 98 is transferred to this heat sink 96, for example, via regions of the bottom surface of this heat sink 96, having close thermal coupling with the peltier 97.
Incidentally, the above thermal conductivity between the peltier 97 (the laser diode 98) and each part of the bottom surface of the heat sink 96 can be made uniform, for example, when a single chamber into which a coolant is injected and whose atmospheric pressure is set at a predetermined value is formed to occupy the whole area inside the flat heat pipe 95.
However, mechanical strength of the flat heat pipe 95 in which this chamber is formed is lowered to a great extent unless the flat heat pipe 95 is formed of a strong material or is formed to have a large thickness. Furthermore, a prescribed value is not always obtained in efficiency of heat exchange achieved by the flat heat pipe 95 since adequate capillary attraction (capillary pressure) for promoting recirculation of the heat medium inside the chamber is not gained.
Moreover, in the conventional example, the flat heat pipe 95 is joined with the surface of the corresponding outer wall of the case 90C and the bottom surface of the heat sink 96 via adhesive, which requires many man-hours in its assembly and brings about restrictions not only on decrease in thermal conductivity due to applicable adhesive but also on reduction in total thickness, and consequently, a prescribed cooling capacity is not always achieved.
However, improvement in reliability and performance, cost reduction, and downsizing are not only objects of nodes to which the aforesaid wavelength-division multiplexing method is applied but also objects common to various equipments such as the tunable OS 90 whose temperature is to be precisely controlled, and therefore, there has been a strong demand for a technique flexibly applicable to high density assembly of various devices.
Incidentally, a prescribed cooling capacity can be achieved by forming the cases 94C and 90C of metallic material having high thermal conductivity such as copper alloy.
However, since such metallic material generally has a large specific gravity and is higher cost compared with aluminum and the like, it has been difficult to be applied in practical use.
Furthermore, the aforesaid decrease in thermal conductivity due to the adhesive is avoidable, for example, when the peltier 97 and the cases 94C and 90C have close thermal coupling with the flat heat pipe 95 via a metallic screw or the like.
However, when a hole through which the above screw is to pass (or to be screwed) is formed in the flat heat pipe 95, the aforesaid channels should be formed not to pass this hole.
Consequently, the channels are prevented from being formed linearly to cause structure complexity, and furthermore, since a place where the threaded hole is to be formed is originally a region which should have close thermal coupling with the channels (the heat medium), it is highly possible that the cooling capacity decreases more as the diameter and the number of the screws to be applied are larger.
It is an object of the present invention to provide a thermal diffuser and a radiator flexibly adaptable to various devices as subjects of temperature control and capable of achieving the temperature control highly efficiently without causing great increase in cost.
It is another object of the present invention to realize efficient and stable thermal diffusion or concentration without decreasing mechanical strength.
It is still another object of the present invention to realize efficient radiation of heat compared with a case in which a large amount of the heat is transferred to one specific region of a joint surface with a thermal diffuser.
It is yet another object of the present invention to realize flexible adaptability to various modes of maintenance and operation, and to suppress factors, such as the vaporization, expansion, coagulation, and so on, of a heat medium which may possibly occur according to temperature and atmospheric pressure and obstruct the process of assembly and mounting.
Moreover, it is yet another object of the present invention to improve efficiency in thermal diffusion compared with a case in which density of a channel formed in a region near a device or a circuit to undergo heat exchange is low.
Furthermore, it is yet another object of the present invention to reduce the cost and simplify the configuration.
Moreover, it is yet another object of the present invention to improve efficiency and responsiveness in heat diffusion.
Furthermore, it is yet another object of the present invention to realize flexible adaptability to the shape and size of an electronic component to greatly ease restrictions on thermal design and mounting of an equipment which includes the electronic component.
Moreover, it is yet another object of the present invention to improve efficiency and responsiveness in thermal diffusion compared with a case in which no capillary attraction acts on a heat medium.
Furthermore, it is yet another object of the present invention to realize flexible adaptability to various shapes and layouts of an electronic component and to ensure close thermal coupling between the electronic component and a channel.
Moreover, it is yet another object of the present invention to maintain total high reliability.
Furthermore, it is yet another object of the present invention to maintain high efficiency and stability in thermal diffusion.
Moreover, it is yet another object of the present invention to ease restrictions on design, manufacturing, maintenance, and operation of an equipment and a system to which the invention is applied, and to improve and stably maintain the performance and reliability of the equipment and the system.
The above-described objects are achieved by a thermal diffuser having a plate-shaped structure which can be welded or bonded to the case of an electronic component to undergo heat exchange with an exterior and has a channel formed in mesh by a plurality of protrusions and through which a heat medium confined in the interior recirculates.
In the thermal diffuser as structured above, the channel through which the heat medium recirculates can be stably formed as long as the strength of the channel against a difference in atmospheric pressure between its interior and exterior and against a physically given force from the exterior is secured by the aforesaid welding or bonding.
The above-described objects are also achieved by a thermal diffuser which is structured as a housing having an outer wall capable of being thermally coupled with the case of an electronic component to undergo heat exchange with an exterior.
In the thermal diffuser as structured above, a channel through which a heat medium recirculates can be stably formed as long as the strength of the housing against a difference in atmospheric pressure between its interior and exterior and against a physically given force from the exterior is secured by protrudingly disposing the aforesaid protrusions on the inner wall of the housing.
The above-described objects are also achieved by a thermal diffuser which is structured as a frame formed integrally with the case of an electronic component which is to undergo heat exchange with an exterior.
In the thermal diffuser as structured above, a channel through which a heat medium recirculates is stably formed as long as the strength of the frame against a difference in atmospheric pressure between its interior and exterior and against a physically given force from the exterior is secured by protrudingly disposing the aforesaid protrusions on the inner wall of the frame.
The above-described objects are also achieved by a thermal diffuser which is provided with a heat medium injection path used for injecting the heat medium to the channel from the exterior.
In the thermal diffuser as structured above, it is possible to freely exchange, inject and add the heat medium to the channel as long as the heat medium injection path can be opened and closed.
The above-described objects are also achieved by a thermal diffuser in which the channel is thickly formed in a region near a device or a circuit which is to undergo heat exchange.
In the thermal diffuser as structured above, the more thickly formed the channel is, the closer thermal coupling with the electronic component the heat medium injected into the channel has.
The above-described objects are also achieved by a thermal diffuser in which the channel is formed with uniform density in a region distant from a device or a circuit which is to undergo heat exchange.
In the thermal diffuser as structured above, the configuration simplification and cost reduction can be realized by standardizing the layout of sections of the channel other than a section closely thermally coupled with the electronic component.
The above-described objects are also achieved by a thermal diffuser in which a channel is also formed between all or a part of the top parts of the plurality of protrusions and the inner wall.
In the thermal diffuser as structured above, a bypass is formed in the channel via all or a part of the top parts of the protrusions so that the heat medium injected into this channel is swiftly diffused and recirculates via a channel consisting of the channel and the bypass arranged in mesh.
The above-described objects are also achieved by a thermal diffuser in which all or a part of the plurality of protrusions are formed in a partially contracted pillar or wedge shape.
In the thermal diffuser as structured above, the channel is formed with high density or formed in mesh even when the aforesaid inner wall is small, as long as molding of the protrusions is possible.
The above-described objects are also achieved by a thermal diffuser in which the ingredients, shapes, and sizes of the plurality of protrusions and/or the inner wall are determined to allow capillary attraction acting on the heat medium in the channel to exceed attraction acting on the heat medium.
In the thermal diffuser as structured above, it is able to enhance efficiency and responsiveness in thermal diffusion compared with a case in which no capillary attraction acts on the heat medium.
The above-described objects are also achieved by a thermal diffuser which comprises a medium poured in all or a part of sections of the channel, for increasing capillary attraction acting on the heat medium in the channel.
In the thermal diffuser as structured above, the more capillary attraction increases, the further promoted the recirculation of the heat medium in the channel is.
The above-described objects are also achieved by a thermal diffuser which has, in all or a part of the plural protrusions, a hole formed capable of joining and/or coupling the thermal diffuser with the case of the electronic equipment or a member used for fastening the thermal diffuser in order to maintain thermal coupling with the case.
In the thermal diffuser as structured above, the hole is formed in a desired protrusion which is to be joined or coupled with the aforesaid member or the case.
The above-described objects are also achieved by a thermal diffuser which comprises a member formed integrally with all or a part of the plurality of protrusions and capable of joining and/or coupling the thermal diffuser with the case or a member used for fastening the thermal diffuser in order to maintain thermal coupling with the case of the electronic component.
In the thermal diffuser as structured above, the member is integrally formed with a desired protrusion which is to be joined or coupled with the member or the case.
The above-described objects are also achieved by a thermal diffuser in which a total amount of the heat medium is determined to be an amount which enables the heat medium to steadily recirculate in a part of the channel having the closest thermal coupling with the electronic component.
In the thermal diffuser as structured above, the heat exchange is stably and continuously performed via the heat medium.
The above-described objects are also achieved by a thermal diffuser in which the outer wall has a region as a thermal conduction path for transferring heat to a specific member, the region with a shape and an ingredient such that the degree of thermal coupling with the specific member becomes a desired value.
In the thermal diffuser as structured above, it is avoided that the thermal resistance increases undesirably due to deviation and distortion in the shape of the outer wall.
The above-described objects are also achieved by a radiator which comprises any of the above thermal diffusers and a heat radiating member for radiating heat transferred via the thermal diffuser to an exterior.
In the radiator as structured above, the heat is diffused via a case and a heat medium injected into the channel formed in mesh, and it is transferred to the heat radiating member without a large amount of the heat being diffused to one specific region of the outer wall of the thermal diffuser.
The above objects are also achieved by a radiator in which a heat radiating member is integrally formed with the thermal diffuser.
In the radiator as structured above, the above heat is diffused via a case and a heat medium injected into the channel formed in mesh , and it is transferred to the heat radiating member without a large amount of the heat being diffused to one specific region of the outer wall of the thermal diffuser.